Final answer:
To flatten the tire plug, use a roller or a similar tool to remove air bubbles and secure the plug flush to the tire, ensuring a proper seal and reliable repair.
Step-by-step explanation:
To flatten the tire plug with a roller or a similar tool is necessary to remove all of the air bubbles and secure it flush to the tire. This step is crucial in tire repair as it ensures that the plug properly adheres to the tire, preventing any future leaks. After inserting the tire plug into the damaged area of the tire, using a roller, like a tire plug roller or even the handle of the plug insertion tool, you press and smooth over the plug. The rolling action helps eliminate any trapped air that might prevent the adhesive from creating a good seal, ensuring the plug is fully integrated into the tire's structure for a reliable repair.